NAME
    "IO::Ppoll" - Object interface to Linux's "ppoll()" call

SYNOPSIS
     use IO::Ppoll qw( POLLIN POLLOUT );
     use POSIX qw( sigprocmask SIG_BLOCK SIGHUP );

     my $ppoll = IO::Ppoll->new();
     $ppoll->mask( $input_handle => POLLIN );
     $ppoll->mask( $output_handle => POLLOUT );

     $SIG{HUP} = sub { print "SIGHUP happened\n"; };
     sigprocmask( SIG_BLOCK, POSIX::SigSet->new( SIGHUP ), undef );

     # If a SIGHUP happens, it can only happen during this poll
     $ppoll->poll( $timeout );

     $input_ev = $poll->events( $input_handle );

DESCRIPTION
    "IO::Ppoll" is a simple interface to Linux's "ppoll()" system call. It
    provides an interface that is drop-in compatible with IO::Poll. The
    object stores a signal mask that will be in effect during the actual
    "ppoll()" system call and has additional methods for manipulating the
    signal mask.

    The "ppoll()" system call atomically switches the process's signal mask
    to that provided by the call, waits identically to "poll()", then
    switches it back again. This allows a program to safely wait on either
    file handle IO or signals, without needing such tricks as a
    self-connected pipe or socket.

    The usual way in which this is used is to block the signals the
    application is interested in during the normal running of code. Whenever
    the "ppoll()" wait is entered the process signal mask will be switched
    to that stored in the object. If there are any pending signals, the
    Linux kernel will then deliver them and make "ppoll()" return -1 with
    "errno" set to "EINTR". If no signals are pending, it will wait as a
    normal "poll()" would. This guarantees the signals will only be
    delivered during the "ppoll()" wait, when it would be safe to do so.

CONSTRUCTOR
  $ppoll = IO::Ppoll->new()
    Returns a new instance of an "IO::Ppoll" object. It will contain no file
    handles and its signal mask will be empty.

METHODS
  $mask = $ppoll->mask( $handle )
    Returns the current mask bits for the given IO handle

  $ppoll->mask( $handle, $newmask )
    Sets the mask bits for the given IO handle. If $newmask is 0, the handle
    will be removed.

  $ret = $ppoll->poll( $timeout )
    Call the "ppoll()" system call. If $timeout is not supplied then no
    timeout value will be passed to the system call. Returns the result of
    the system call, which is the number of filehandles that have non-zero
    events, 0 on timeout, or -1 if an error occurred (including being
    interrupted by a signal). If -1 is returned, $! will contain the error.

  $bits = $ppoll->events( $handle )
    Returns the event mask which represents the events that happened on the
    filehandle during the last call to "poll()".

  $ppoll->remove( $handle )
    Removes the handle from the list of file descriptors for the next poll.

  @handles = $ppoll->handles( $bits )
    Returns a list of handles. If $bits is not given then all of the handles
    will be returned. If $bits is given then the list will only contain
    handles which reported at least one of the bits specified during the
    last "poll()" call.

  $sigset = $ppoll->sigmask
    Returns the "POSIX::SigSet" object in which the signal mask is stored.
    Since this is a reference to the object the "IO::Ppoll" object uses, any
    modifications made to it will be reflected in the signal mask given to
    the "ppoll()" system call.

  $ppoll->sigmask( $newsigset )
    Sets the "POSIX::SigSet" object in which the signal mask is stored.
    Usually this is not required, as a new "IO::Ppoll" is initialised with
    an empty set, and the "sigmask_add()" and "sigmask_del()" methods can be
    used to modify it.

  $ppoll->sigmask_add( @signals )
    Adds the given signals to the signal mask. These signals will be blocked
    during the "poll()" call.

  $ppoll->sigmask_del( @signals )
    Removes the given signals from the signal mask. These signals will not
    be blocked during the "poll()" call, and may be delivered while "poll()"
    is waiting.

  $present = $ppoll->sigmask_ismember( $signal )
    Tests if the given signal is present in the signal mask.

SEE ALSO
    *   IO::Poll - Object interface to system poll call

    *   ppoll(2) - wait for some event on a file descriptor (Linux manpages)

    *   IO::Async::Loop::IO_Ppoll - a Loop using an IO::Ppoll object

AUTHOR
    Paul Evans <leonerd@leonerd.org.uk>

